Question

List and briefly describe the errors that may occur with pH measurement

Answer 1

Procedure:

For the measurement a pH meter is used and it is supposed to be calibrated, using standard buffers. The buffer pH is dependent on temperature. The sensor response is dependent on temperature. The sensor needs a time (0.5…3 minutes) for a relatively stable response. The sensor shows a drift ( the measured value is not absolutely stable).

Possible sources of errors:

pH meter is not calibrated recently or is not calibrated at all

the standard buffers used for calibration are depreciated

the used buffers (for calibrtion) are different than the type known by the instrument

The pH was recorded before the stabilization time

The pH was recorded too late after stabilization time (drift possible).

     and if the calibration and measurement temperature are different, also:

      the temperature during calibration or measurement is not observed

the pH variation with temperature (for specific buffers) is not known in the instrument software.

The pH meter is not correcting for temperature, or has no temperature sensor, or the temperaturure value is not introduced correctly.